Some portion of gulshan abad do touch the dha 4 initial phases. The google earth also shows that. I am unsure that in future dha may build a boundary wall and close that route or not.
1- can some expert give his opinion on buying anything, which is near to dha phase 4?
2- what is the price of 5 or 10 marla plot there?
I don't think DHA has any plan to connect DHA-4 with Adiala Road through Gulshanabad. There would surely be a boundary wall, if it's not there already.
The lower side road of Clifton Town (within Gulshanabad geography) is just at the boundary of DHA-4.